fix: add close/context-manager to diagnosis store; tighten import boundary

adapters/baseline_diagnosis_store.py

@@ -10,9 +10,13 @@ from __future__ import annotations
 
 import sqlite3
 from pathlib import Path
+from typing import TYPE_CHECKING
 
 from core.evolution.types import DiagnosisSignalRow
 
+if TYPE_CHECKING:
+    from types import TracebackType
+
 # 表列顺序即 DiagnosisSignalRow 字段顺序（question_id..session_id），
 # upsert 写入与 load 还原共用，避免手写列名两处漂移。
 _COLUMNS: tuple[str, ...] = (
@@ -152,3 +156,18 @@ class SqliteDiagnosisSignalStore:
             )
             for r in cursor.fetchall()
         ]
+
+    def close(self) -> None:
+        """关闭底层 SQLite 连接，释放文件描述符与锁。"""
+        self._conn.close()
+
+    def __enter__(self) -> SqliteDiagnosisSignalStore:
+        return self
+
+    def __exit__(
+        self,
+        exc_type: type[BaseException] | None,
+        exc_val: BaseException | None,
+        exc_tb: TracebackType | None,
+    ) -> None:
+        self.close()